Engage: Observing Soil

Explore: Water Retention

Follow the directions on Explore: Investigating Soils. You will need to download and print this page by going to Related Items and then Related Documents at the bottom of this page.

Observe how quickly the water drains, or collects, in the graduated cylinder.

Which type of soil allowed more water to pass through it? Why?

Which type of soil retained, or held, the most water? Why?

Explain: Soil Debrief

Click on the image to learn more about different types of soil and their importance to plant growth.

What did you learn? What are silt and loam?

How are soils different, and what does that mean for plant growth?

Elaborate: Soil and Plant Growth

Observe the sediment jars. What do you see in the soil layers? What’s floating on top?

Click on the image to begin the video. Move the cursor to begin watching the video at 1 minute, 50 seconds.

What are silt and loam? Do you see any of those things in your class sediment jars?

Based on the soil samples in the class sediment jars, what might need to be added to the soil to make it better able to support plant growth?

Evaluate: Soil

To retake the quiz, reload the page and then select "no" when the "Resume Quiz" dialog box appears.

Teacher Notes

Engage
Students' answers regarding soil observations will differ. They should consider color, texture (size of particles that form each soil), and the presence of organic and inorganic matter. Organic matter includes plant and animal remains and living things such as worms, bacteria, fungi, or insects. Inorganic matter includes nonliving things such as rocks, minerals, air, and water. At this time, please do not suggest or define any of these properties. Allow students to brainstorm independently, in pairs, in small groups, or as a class.

The difference between dirt and soil is the presence of organic matter in soil.

Optional Activity:
Provide students with different soils and with handlenses to observe soils.

Explore
Gather materials for students to use in the investigation. The clay needs to be powdery and not clumped together. It may be useful to pulverize clumped clay with a rubber mallet or hammer.

As an alternative to using four graduated cylinders per group, you can substitute 16-ounce or 1-liter clear plastic bottles. Cut the tops off the bottles and invert them in the bottles to use as funnels. Pour the collected water into a graduated cylinder to measure the amount of water.

Download and print Explore: Investigating Soils for each student. Click on Related Items and look under Related Documents to locate this recording sheet.

Divide the class into groups of 3-4 students. Facilitate the activity by walking between the groups as they work. Redirect or answer questions as needed.

Gravel and potting soil will allow the most water to collect in the cylinders because the particles in those soils are larger, leaving more space between them. Water can more easily filter, or pass, between the particles.

Clay will retain, or hold, the most water because its particles are small and powdery. The particles fit together closely, which prevents water from easily passing between them. This means there will be little water collected in that cylinder.

Students may further investigate by using their hands to feel the different soils after the addition of water.

Explain

Silt is another type of soil found along riverbanks. It has particles that are smaller than sand yet bigger than clay. Adding water to silt creates mud. Loam is a combination of sand, silt, and clay. It is preferred for plant growth.

Soils are different depending on their type and where they are located in the world. Some soils are more suitable for plant growth than others. The most fertile soils have the right combination of sand, silt, and clay. Space between particles fills with air, allowing plants to breathe. Fertile soils also need organic and inorganic matter. Decomposers, such as worms, bacteria, and fungi, help aerate and return nutrients from decaying plant and animal material to the soil.

Instruct students to click on the animation to review the vocabulary terms collect/collection and retain/retention. They will drag the words and definitions to the appropriate boxes.

Water that is held in soil is defined as being retained or as water retention.

Water that filters, drains, or is transmitted through soil is defined as being collected or as water collection.

Instruct students to click on the animation to review the vocabulary terms inorganic and organic matter. They will drag the descriptions and drop them onto the matching vocabulary word.

Inorganic matter includes nonliving things, such as air and water.

Organic matter includes living or once living organisms, such as decaying plant and animal matter and decomposers.

Elaborate
Collect two or three soil samples from different areas and as many jars. You could ask students to bring soil samples from home if you like. Place a different soil sample in each jar. The soil should fill about 1/3 to 1/2 of the jar. Add enough water to fill the jar to about 2/3 to 3/4 full.

Ask a student to shake the jars, set them down, and make observations. They should eventually see the layers settle out, the organic matter begin to float, and bubbles form on the surface of the water. The bubbles are a result of air escaping the soil. Soil samples from different areas may have different amounts of gravel, sand, clay, silt, and organic matter.

Instruct students to click on the image to begin the video. They can fast forward the video or move the cursor to begin the video at 1 minute, 50 seconds.

Silt is a finer soil than sand. It can be found along riverbanks and creates a soft mud when combined with water.

Loam is a combination of sand, silt, and clay that is preferred for plant growth.

Student answers regarding what might need to be added to the soil to support plant growth will vary based on soil samples.

Evaluate
The quiz has five questions. Students will have three attempts to correctly answer a question before the next question is introduced. Each question provides the student with immediate feedback. Following the completion of the quiz, students may review the quiz to view correct and incorrect answers.

Answer Key
1. The top picture (gravel) should be matched with rocky and largest particles. The second picture from the top (potting soil) should be matched with fertile and brownish black. The third picture from the top (sand) should be matched with grainy and gritty and tan or beige. The bottom picture (clay) should be matched with reddish orange, powdery, and smallest particles.
2. Air, decaying leaves, decomposers, nutrients, and water are all things that help soil support plant growth.
3. Clay retains, or holds, the most water. This occurs because there is not much space between the particles.
4. Soil C because it retains the most water. This question is similar to number 3 but asked in a different way. Students must pay attention to the data table and the picture to answer the question.
5. The soil could be sand found in a desert where water is initially retained close to the surface. Desert-dwelling plants often have shallow roots that allow them to absorb water quickly since it does not rain much. Again, students must analyze the data to properly answer the question.